MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistor) are the most widely used form of transistor today. MOSFETs function as discrete components as well as form the basis of complex Integrated Circuits (ICs). The MOSFET generally has three terminals, namely, a source, a drain and a gate, where the gate serves to define a conducting channel between the drain and source terminals to control current flow between them. The structure of such MOS devices is obtained by growing different metal layers on top of a silicon layer.
Largely, MOS devices are made from the standard industrial CMOS (Complementary metal-oxide-semiconductor) process in which the source and drain are connected at the surface of the wafer. Such conventional transistors utilize the horizontal and vertical pattern of metallization where all layers are interconnected with each other, with the top layer being connected to pins on the IC through wires. In such designs, the length of the interconnectivity wires increases the complexity of the device since current has a longer path to flow in the device. Other existing solutions define the transistor structure with multiple metal layers as bottom layers, middle layers, and top layers. The lower metal layers are connected to the source and the drain regions. The middle layers are connected with each other and are further connected to the source region. The top metal layers are tied together and are connected to the drain region through openings in the middle layers. The main disadvantage of such a design is that they result in a high resistance and the resistance cannot be reduced beyond a certain value or limit. Although low interconnect resistances can be achieved with the existing solutions, they do not allow reducing the resistance beyond a certain minimum level. Thus, there is a need to design a transistor to overcome the discussed limitations.